1. Field of the Invention
The present invention relates generally to display devices, and more particularly to large-screen proJection display apparatus incorporating a thin display panel for use in producing an image of high resolution for projection onto a viewing screen. The invention also relates to active-matrix color liquid crystal display devices for use in color image projector systems.
2. Description of the Prior Art
Conventionally, display devices using a liquid crystal display (LCD) panel are well known for use in large-screen color image projector systems. The display devices of this type are designed to produce a picture image for display on an associated viewing screen by modulation of light rays using the optical characteristics of liquid crystal materials as sealed in the LCD panel. The presently available LCD display devices come with a display area consisting of an array of rows and columns of picture elements or "pixels" as organized into a planar matrix form; for example, a matrix of 640 by 480 dots having a horizontal array of 640 pixels and vertical array of 480 pixels.
Typically, the LCD display devices are driven in such a manner that information bits are written at respective pixels arrayed in a matrix while sequentially scanning the same causing the liquid crystal at an intended pixel to change in optical response characteristic to finally attain display of a picture image on the screen.
One prior known LCD display scheme on an associated screen is illustrated in FIG. 5, which is of an active-matrix LCD panel with a matrix of m x n pixels, where "m" and "n" are integers. The display operation thereof is as follows. Information is first written into a selected pixel at the upper left address (0, 0) in the uppermost row on the display screen. Then, information is written into its adjacent pixel at a successive address (1, 0). Such writing of information will be sequentially performed with respect to the remaining pixels in the first row while these are being subject to scanning.
After completion of information writing for the first row of pixels, similar write operation is then sequentially carried out with respect to the following, second row of pixels. In this way, the sequential write operation will be repeated up to the final pixel row on the LCD screen of FIG. 5. In the information write procedure formation of one display image is terminated upon completion of information write with respect to the "last" pixel with address (m, n) as located at the lower right corner of the display screen. A resultant one-screen image is called the "frame." Typically, this frame will be rewritten or "refreshed" on the screen for thirty times per second.
To attain the aforesaid simple sequential write operation for LCD display, peripheral driver circuitry (generally integrated on an IC chip) is employed which serves to store data representative of every horizontal line image and to supply such stored one-line scan image data to a corresponding part of active-matrix region with each horizontal line as a unit. This display drive technique is known as the "line sequence" scheme in the art.
As a further advanced arrangement, an LCD display device is known which incorporates an active-matrix region(s) and associative peripheral driver circuits, all of which are integrated on a single substrate that may be made of silicon, glass, or the like. This may enable accomplishment of reduction in thickness and in size, resulting in a decrease in manufacturing cost. However, the prior art is encountered with a serious problem in that the operation frequency is extraordinarily increased forcing the peripheral circuits to operate at higher rate accordingly. In other words, as the operation frequency required for associative horizontal scanning controller circuits becomes equivalent to (m.times.n.times.30) Hz, it is required that the controllers operate at extra high speed. By way of example, in the case of a 640.times.480 dot active-matrix region, it should be required that the horizontal scan controller operate at approximately 10 MHz rate or higher in order to achieve successful horizontal scanning of the active-matrix region.